I'm not entirely sure, but it looks like some people might not like
jokes about the Holocaust.
On a more serious note, the project has become more serious over
the 7 or so years of its existence.
Replaces the inaccurate Rec. 709 luma we used to use before.
This is the first feature here that requires libm, which doesn't
seem to be a particularly great sacrifice.
Moreover, I've rectified that the input isn't linear in sRGB,
and then was even normalized wrong for the luma formula.